It is the biggest haul so far by any member of Silicon Valley’s “11-digit club,” those companies that have gained valuations of at least $10 billion. Among them are Airbnb, the home-rental site; Dropbox, the online file-storage provider; and Xiaomi, a Chinese handset maker.

But Uber’s new net worth, which excludes the latest round of money, is one of the highest ever attained by a start-up.

Behind the soaring numbers is the hunger of investors with money to burn who are eager for a piece of fast-growing companies. About $10.7 billion was invested into start-ups in the first three months of the year, the most in at least three years, according to Dow Jones VentureSource.

Much of that money has gone into the biggest businesses in their markets, with investors betting that they will continue to post enormous growth. But some second-place players are cashing in, too: Lyft, a smaller car service provider, raised money from investors like the Chinese e-commerce giant Alibaba Group at a roughly $700 million valuation earlier this year.

Still, few companies have proved as alluring to would-be financial backers as Uber, which four years ago pioneered a new kind of business model, one in which a start-up replaced a part of users’ daily lives. Its service allows users to call up cars from their smartphones, a category that has swelled with imitators and competitors like Lyft, which operates in dozens of cities.

But Uber, co-founded by its chief executive, Travis Kalanick, remains the king of the hill it created. It now runs in 128 cities in 37 countries around the world. And though it began as a dispatch network for professional chauffeurs in Town Cars and S.U.V.s, its most prominent offering is UberX, where drivers use their own cars.

Its prevalence has prompted some users, including high-powered financial executives, to give up their cars and rely solely on the service for their driving needs.

“Uber is changing the fabric of these cities,” Mr. Kalanick wrote in a company blog post. He added: “With our growth and expansion, the company has evolved from being a scrappy Silicon Valley tech start-up to being a way of life for millions of people in cities around the world.”

Since it is still privately held, Uber does not need to disclose its financials. But Mr. Kalanick told The Wall Street Journal on Friday that the service, which collects a roughly 20 percent commission from its drivers, doubled in revenue every six months.

It is that extreme growth that has drawn in financial firms with deep pockets. The latest fund-raising effort was led by Fidelity Investments and included Wellington Management, Summit Partners, BlackRock and Kleiner Perkins Caufield & Byers. Existing investors like Google Ventures and Menlo Ventures also participated.

Mr. Kalanick himself has hit pay dirt with Uber. His first venture, a search engine created while he was still in college, filed for bankruptcy within three years. Akamai Technologies bought his second for $19 million.

The new money Uber has raised could come in handy as it battles competitors. The company and Lyft are dueling for dominance in more than a dozen cities, with each dropping prices to woo customers.

But the oversize new funding round goes hand in hand with Mr. Kalanick’s ambitions for the company. Not content to stick with arranging car rides, the 37-year-old entrepreneur has talked about creating a logistics network where its drivers ferry goods around cities. One of its nascent experiments is running a courier service in New York City known as Uber Rush.

By setting up shop in the real world, however, Uber has bumped up against tenacious interest groups determined to defend their turf. The service notoriously has battled the taxi commission in Washington, with Mr. Kalanick deriding one set of rule changes as “taxi protection at its finest.” And taxi drivers in Chicago and other cities are seeking to form a national union, in part to battle the success of Uber and other services.

Mr. Kalanick said at ReCode’s Code Conference last week that his company was in a political campaign, and called the taxi industry his opponent.

But the company said it had more work to do. In his blog post, Mr. Kalanick wrote: “This ‘Uber’ way of life is really a reflection of our mission to turn ground transportation into a seamless service and to enable a transportation alternative in cities that makes car ownership a thing of the past.”

Video

Questions of Responsibility at Uber

In January, The New York Times interviewed Uber’s C.E.O., Travis Kalanick, about the ride-sharing company’s business practices, including liability in accidents.

By Sean Patrick Farrell on Publish Date January 26, 2014.
Photo by Jack Atley for The New York Times.